/*
    Calculate Circle Area using Java Example
    This Calculate Circle Area using Java Example shows how to calculate
    area of circle using it's radius.
*/

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class CalculateCircleAreaExample {

    public static void main(String[] args) {
           
            int radius = 0;
            System.out.println("Please enter radius of a circle");
           
            try
            {
                    //get the radius from console
                    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
                    radius = Integer.parseInt(br.readLine());
            }
            //if invalid value was entered
            catch(NumberFormatException ne)
            {
                    System.out.println("Invalid radius value: " + ne);
                    System.exit(0);
            }
            catch(IOException ioe)
            {
                    System.out.println("IO Error :" + ioe);
                    System.exit(0);
            }
           
            /*
             * Area of a circle is
             * pi * r * r
             * where r is a radius of a circle.
             */
           
            //NOTE : use Math.PI constant to get value of pi
            double area = Math.PI * radius * radius;
           
            System.out.println("Area of a circle is " + area);
    }
}

/*
Output of Calculate Circle Area using Java Example would be
Please enter radius of a circle
19
Area of a circle is 1134.1149479459152
*/


